General aviation carburetor testing with turbocharger and analysis device

ABSTRACT

A testing device for general aviation carburetors and fuel servos. The testing device is capable of replicating carburetor operating characteristics operation under both naturally aspirated conditions and turbo charged compressed air conditions using sensors to monitor and record the operating characteristics of both horizontal and vertical type carburetors, and compare the data received with predefined values. The testing device measures both test fluid and air flow through a carburetor. A moveable camera is placed within the throttle body of the carburetor being tested providing visual inspection of the fluid atomization with snap shot capability. The testing device also includes flow sensors to record the performance of the carburetor, providing automated data collection with memory storage. The device is fully portable with lockable caster wheels.

PRIORITY CLAIM

In accordance with 37 C.F.R. § 1.76, a claim of priority is included inan Application Data Sheet filed concurrently herewith. Accordingly, thepresent invention is a continuation-in-part and claims priority to U.S.patent application Ser. No. 16/058,689, entitled “GENERAL AVIATIONCARBURETOR TESTING AND ANALYSIS DEVICE”, filed Aug. 8, 2018 whichfurther claims priority to U.S. Provisional Patent Application No.62/543,147, entitled “GENERAL AVIATION CARBURETOR TESTING AND ANALYSISDEVICE”, filed Aug. 9, 2017; the contents of which is incorporatedherein by reference.

FIELD OF THE INVENTION

This invention is directed to the field of portable test benches, and inparticular to a self-contained test bench for analyzing carburetors,turbos and fuel servos used in general aviation aircraft.

BACKGROUND OF THE INVENTION

Internal combustion engines employ a fuel servo or carburetor forpreparation of an air-fuel mixture required for the combustion process.A fuel servo meters pressurized fuel which is directed to fuelinjectors. A carburetor prepares an air-fuel mixture. For simplicity ofdiscussion, this disclosure will be directed to carburetor testing andanalysis but it is noted that the instant device works equally as wellwith fuel servos.

In General Aviation (“GA”) airplanes, a carburetor also includes aprovision to adjust the air-fuel mixture for various conditionsincluding change in density altitude. Optimum performance of a GA enginewith a constant speed propeller may be determined by monitoring theExhaust Gas Temperature (EGT). For instance, the slower burningcharacteristics of a lean mixture will cause the heat of combustion tocontinue further into the power stroke and EGT peaks lean ofstoichiometric. Enriching the mixture, e.g. minus 125 degrees Fahrenheitrich of peak EGT, will produce the best power. When an air-cooledaircraft engine is running at normal power, if fuel is slowly added tothe stoichiometric mixture it will have a cooling effect and thecombustion gas and cylinder head temperature will decrease. Onnon-constant speed propellers, RPM may be used as an indication ofpower.

A GA carburetor must operate within design specifications to meet theneeds of the engine and for the safety of the airplane occupants. Forthese reasons carburetors are tested to when they are new, at a time ofrebuilding, or during preventative maintenance reviews. In operation, afloat carburetor employs a chamber that is filled with fuel using thefloat to regulate the amount of stored fuel. Fuel from the float chamberis drawn into the carburetor by a venturi using a metered jet. In thethroat of the carburetor, air pressure is dropped in accordance withBernoulli's principle wherein fuel is introduced into the induction airbefore the entry into the cylinders for the combustion process. A mainfuel jet outlet is used so that the fuel can atomize and diffuse to themaximum extent possible. An air bleed can be used so that air bubblesare introduced to improve vaporization of the fuel.

When the throttle is nearly closed on a carburetor, the airstream flowdecreases to an extent that the fuel flow through the main jet becomesunresponsive. At this closed throttle position there remains an air gapwhere the throttle valve almost touches the wall of the carburetorthroat wherein an idling jet is used to provide a proper fuel/airmixture. Manual mixture control of GA carburetors is needed because athigher altitudes the volume of air is the same but its density is less.Therefore, the amount of fuel must be reduced to prevent the mixturefrom becoming too rich. The above illustrates that a GA carburetor maybe simple in concept, but each carburetor may have uniquecharacteristics that can enhance performance when operating correctly ordetract from the performance if out of calibration for its respectiveengine.

As with any mechanical device, a carburetor must be checked for properoperation both at the time of manufacture and during any engine rebuildoperation. In addition, a carburetor may malfunction in between the dateof manufacture and date of engine rebuild. A carburetor usedinfrequently may have spoiled fuel which can gum up the jets and floatbowl. A carburetor used in an adverse environment may suffer frompremature gasket failure.

Due to the inherent problems that can occur with an aircraft carburetorthat is not operating properly, it is imperative that any carburetorplaced into service is tested. While carburetor test benches are knownin the industry, what is needed in the industry is a diagnostic testbench that is self-contained, portable, and capable of resembling engineoperational characteristics with the ability to view actual operationand document all carburetor operational characteristics.

SUMMARY OF THE INVENTION

Disclosed is a testing device for general aviation carburetors. Thedevice includes a vacuum pump that is capable of duplicating theairstream flows through a carburetor with meters measuring the air-testfluid operational characteristics of the carburetor. Test fluid isintroduced into the airstream flow by the carburetor jets. A quickrelease clamp allows attachment of either vertical or horizontal typecarburetors including those from AVStar Fuel Systems; Marvel Schebler,Precision Airmotive and the like. A pump delivers test fluid to thecarburetor under test conditions wherein the operational characteristicsare viewed and analyzed. The testing device includes sensors to recordthe performance of the carburetor providing automated data collectionwith memory storage. A throttle body placed camera is positioned withinthe carburetor throat to provide visual inspection of the atomizationwith snap shot capability.

After the air-fluid mixture is passed through the carburetor, test fluidis separated from air stream by a two-stage separator. The device isfully portable with lockable caster wheels.

An objective of the invention is to disclose an improved test benchconstructed specifically for general aviation carburetors.

Another objective of the invention is to disclose a general aviationcarburetor diagnostic test bench having a liquid separator that usesdrip edges for optimum separation of test fluid from air.

Still another objective of the invention is to disclose a generalaviation carburetor diagnostic test bench having vacuum capable ofreplicating an internal combustion engine air draw to effectuate theventuri operation of a carburetor from idle air flows up to rated airflows.

Yet still another objective of the invention is to disclose a generalaviation carburetor diagnostic test bench having a camera probing acarburetor throttle body to provide visual inspection of the carburetoroperation, the camera capable of taking video or still shots forperformance recording.

Another objective of the invention is to disclose a general aviationcarburetor diagnostic and testing bench having quick release clamps forsecuring either a horizontal or a vertical type carburetor to the bench.

Still another objective of the invention is to provide an improved testbench for general aviation carburetors that is compact in size allowingtrue portability by inclusion of caster wheels for ease of movement.

Other objectives and further advantages and benefits associated withthis invention will be apparent to those skilled in the art from thedescription, examples, and claims which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the general aviation carburetor testingand analysis device of the instant invention;

FIG. 2 is an enlarged perspective view of the front panel;

FIG. 3 is left side view thereof with the side panel removed;

FIG. 4 is a cross sectional side view of FIG. 3 showing the intake aircircuit;

FIG. 5 is a cross sectional view of a carburetor tested in the verticalposition;

FIG. 6 is a cross sectional view of a carburetor tested in thehorizontal position;

FIG. 7 is an exploded view illustrating the various adapters used fortesting fuel systems in the vertical position;

FIG. 8 is a right side view thereof with the side panel removed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A detailed embodiment of the instant invention is disclosed herein.Specific functional and structural details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representation basis for teaching one skilled in the art to variouslyemploy the present invention in virtually any appropriately detailedstructure.

Referring now to the drawings, the general aviation carburetor testingand analysis device 10 of the instant invention consists of a frameassembly encompassed by a back panel 12, a top panel 14, a bottom panel16, a left side panel 18, a right-side panel 20, and a frontal section22. The frontal section 22 includes a bench top weldment 24 housing anintake plenum 26 with a camera scope 28 extending through the intakeplenum 26. The frame assembly consists of vertical 120 and horizontal122 supports constructed and arranged to support the above-mentionedpanels and internal components. The frame assembly is lightweight andcompact, allowing portability by use of castor wheels.

The frontal section 22 is further defined with an air pressure gauge 30and a test fluid pressure gauge 32. A video monitor 34 displays imagesfrom the camera scope 28. A monitor 46 is coupled to a computer systemthat has stored predetermined values for use in comparing the carburetorbeing tested versus a base line which characterizes the proper operationof a new carburetor. Software includes the ability to monitor all keyaspects of any test regarding air and test fluid flow, and record alltest conditions and results for tracking by serial or other referencenumber. A horizontal air port 36 is available for use with horizontalstyle carburetors using a port plug 38′ for sealing the verticalextension port 44 when not in use. A vertical air port 40 includes apipe member 42 having a 90-degree bend for positioning a 4″ verticalport extension 44 directly above intake plenum 26. For illustrationpurposes, a carburetor 200 is secured to the intake plenum 26 with anupper portion of the carburetor 200 secured to the vertical portextension 44. Horizontal port 36 includes plug 38 to prevent airflowthrough the bottom circuit.

A regenerative vacuum pump 50 introduces an airstream through the intakeplenum 26 pulling air through the carburetor 200 for testing. Theimpeller based vacuum 50 is oil free and provides a continuous airstreamusing anti-sparking cast aluminum housing. External power is supplied tothe vacuum pump 50, test fluid pump 100 and diagnostic equipment byattachment through electrical plug 52. The vacuum pump 50 permitstesting to replicate a high rpm power operation such as that produced byan aircraft engine operating up to 2,700 rpm, or a low speed load suchas that produced by an aircraft engine operating at idle between 600-700rpm. An airstream is created by pulling air through the carburetor 200with the discharged airstream directed through a transfer pipe 42 beforeentering an intake 54 to the primary liquid separator 56. Test fluidcollected in the primary separator 56 is directed through a fluidcollection tube leading to a test fluid storage tank 60. A coupling 62connects the outlet of the primary liquid separator 56 to the intake ofa secondary liquid separator 66, the secondary separator 66 polishingthe airstream by also draining any remaining test fluid from theairstream directed to the test fluid storage tank 60 by fluid collectiontube 68. Both collection tubes make use of a check valve 64 which isnormally open and closed under vacuum. The secondary separator 66 havinga coupling 70 routed to the vacuum 50 by transfer pipes 94 essentiallyproviding a closed loop circulation.

The horizontal air port 36 and the vertical air port are adjoined by wye72. The ports 36, 40 exhaust the carburetor depending on whether thecarburetor being tested is a horizontal or vertical type. When testingvertical type plug 38 is utilized preventing airflow.

The primary separator 56 includes a screen element 80 positioned withina housing 74 which is coupled to a base 76 with quick release couplers78. A drip screen 82 is provided from a baffle having a drip edge 84located along a lower portion of the drip screen. The drip edge 84 isconstructed and arranged to create a laminar flow surface which causesthe reduction and/or removal of atomized test fluid from the airstream.The airstream impacting the drip screen 82 causes test fluid to beseparated from the airstream, the buildup of test fluid on the surfaceof the drip screen helps attract additional fluid for enhanced recovery.Similarly, the secondary separator 66 includes a filter element 88positioned within a housing 86 and coupled to a base with quick releasecouplers 90. A drip screen 92 may also be added but is not needed in thepreferred embodiment as the secondary filter operates as a polishingfilter.

The test fluid storage tank 60 provides a continuous flow of fluidthrough an inline valve 96, followed by a filter 98, coupled to a fluidpump 100 which is fluidly coupled to the carburetor 200 by a controlvalve 102 located on the front panel. The control valve routes the testfluid through the appropriate circuit depending on what type of fuelsystem or fluid pressure is required. For GA carburetors, fuel pressureis typically less than 8 psi. For GA fuel servos, fuel pressurerequirements can vary but typically require at least 12 psi at idle andrequire proper operation at much higher pressures. The control valvedirects the flow of the test fluid through either an internal pressureregulator providing a pre-set test fluid pressure or through anadjustable pressure regulator 124 on the front of the bench.Furthermore, in the adjustable pressure circuit, an electric boost pump128 can increase the pressure of the test fluid to a level similar tothat seen on a GA aircraft. Said boost pump can be triggered by engagingthe pump using switch 126. An ultrasonic level indicator 104 is used tomonitor the amount of test fluid in the storage tank 60. A flowtransmitter 106 and mass flow meter 108 are used to record the testfluid flow rate. The carburetor 200 receives test fluid flow for fillinga carburetor float chamber for delivery through the carburetor jets. Thepump 100 provides a realistic repeat of a fuel system found on a generalaviation aircraft by employing a general aviation pump. Operation of thecarburetor flow jets can be visually inspected using the monitor 34. Themonitor 34 displays images captured by the camera scope 28 positionedwithin the throttle body of the carburetor being tested.

Used or new carburetors designed for general aviation aircraft frommanufacturers such as AVStar Fuel Systems; Marvel Schebler, PrecisionAirmotive and the like can be viewed internally as well as tested. Forinstance, in determining the flow pattern or amount of wear of themovable parts of a carburetor, the throttle of the carburetor can beviewed in operation using the camera scope 28 which is moveable by anextension 48 within the throttle body of the carburetor being testedwherein the induction passage can be analyzed. Proper as well asimproper fluid flow can be visually inspected. Each carburetor has aninduction passage with a predetermined cross-sectional flow area whichcan be compared to a carburetor that was tested as new. Thatpredetermined area is an area for which, when the carburetor was new,the edge of the throttle was midway along the bypass aperture of theidling circuit. The degree of pressure drawn in the idling circuit ofthe carburetor is then compared with a reference value which is thedegree of pressure which prevails on in a brand-new carburetor operatedunder the same test fluid and air flow conditions. The device includes acontroller having preprogrammed reference values that are checkedagainst the carburetor being tested. This allows used, or new,carburetors to be checked against predetermined reference values. Thesoftware providing a comparison of values that are recorded with thoseprerecorded maintained of each carburetor analyzed under the desiredtest conditions.

The wye 72 allows airflow from a vertical disposed carburetor 200 by useof a tubing element 42 to position the port 44 directly over the intakeplenum 26 as shown in FIG. 5. The vertical adjustment port 44 at the endof the tubing element 42 periscopes to maintain sealing under vacuum foraccommodating different height carburetors using various adapters 130 asshown in FIG. 7. When the vertically disposed carburetor 200 isemployed, a plug 38 is positioned into the horizontal port to prohibitairflow. Referring to FIG. 6, when a horizontal carburetor 200′ isemployed, the vertical port 44 includes plug 38′ to prohibit airflowthrough the tubing element 42. An extension tube 110 is used to couplethe horizontal carburetor 200′ to the intake plenum 26.

The device is vented by use of an external exhaust vent connection 112that permits the separated air to be expressed outside an enclosed area.A cabinet intake vent 114 includes an air filter and is used to vent thecabinet, the cabinet vent 114 can be drawn from inside an enclosedbuilding. A main shut off panel 116 is positioned on the side panel 20.An emergency shut off switch 118 is placed on the front portion 24.

A turbocharger 136 provides an option of testing and analyzingpressurized air. When used with the turbocharger 136 a switch isprovided to simultaneously open a gate valve located at wye 132 tobypass inlet airflow to the vacuum pump 50 which alleviates any strainto the motor and no longer pulling a vacuum through the system. Thisswitch also engages a clutch 134 which interfaces with the motor shaftof the vacuum motor. This clutch engages a belt system to use the motorto drive a turbo 136 at the high rpm required to produce positivepressure. Under normally aspirated bench conditions, check valve 138allows airflow to be pulled through the primary air filter 114 toprovide a vacuum for fuel system testing. When the turbo 136 is engaged,check valve 138 remains closed allowing air to be pulled through thesecondary air filter 140 providing supply air to the turbo 136. Underpositive pressure conditions, check valve 142 opens allowing theconsumed air through the fuel system to be diverted and exhaustedthrough connection 112. Under normally aspirated vacuum conditions,check valve 142 remains closed directing the air through the vacuum pumpwhen the gate valve at location 132 is closed. To limit the maximumallowable pressure provided to a fuel system during testing, pressurerelief valve 144 is employed. The turbocharger 136 compresses the intakeair and forwards the compressed air to the air metering section of thefuel metering device.

It will be apparent to those skilled in the art that various changes maybe made without departing from the scope of the invention, and theinvention is not to be considered limited to what is shown and describedin the specification and any drawings/figures included herein. It willbe recognized in the industry that that while carburetors and fuelservos in GA aircraft must be maintained to the highest standard, otherinternal combustion engines would also benefit from the testing andanalysis device including air boat, motor vehicles, motorcycles,snowmobiles, and so forth.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein.Although the invention has been described in connection with specificpreferred embodiments, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiments.Indeed, various modifications of the described modes for carrying outthe invention which are obvious to those skilled in the art are intendedto be within the scope of the following claims.

What is claimed is:
 1. A portable analyzing device for carburetors andfuel servos used in general aviation comprising: a housing supported bywheels; an intake plenum secured to said housing, said intake plenumconstructed and arranged to receive a carburetor to be analyzed; avacuum pump mounted in said housing, said vacuum pump capable of drawingan airstream through said intake plenum or coupling to a bypass todisable said vacuum pump from drawing an airstream through said intakeplenum; a turbocharger secured to said vacuum pump by a drive belt,rotation of said vacuum pump allowing said turbocharger to producepositive pressure; a junction member having a first end fluidly coupledto an outtake of said turbocharger directing positive pressure to avertical and port extension; a port plug insertable into said horizontalport extension when said vertical port extension is coupled to saidcarburetor or said port plug insertable into said vertical portextension when said horizontal port extension is coupled to saidcarburetor; a fluid pump coupled to a fluid tank and to said carburetorfor transferring a test fluid from said fluid tank to a fluid inlet onsaid carburetor wherein said carburetor injects test fluid into theairstream; a test fluid flow sensor to monitor the amount of fluid drawnfrom the tank; a camera positioned within said intake plenum andinsertable into said carburetor, said camera coupled to a displaymonitor allowing real time viewing of operational aspects of saidcarburetor; a separator for removing test fluid drawn through saidcarburetor, said separator having returning test fluid to said fluidtank; a computer system having a microprocessor and digital storage,said computer system recording operating characteristics of saidcarburetor and comparing said operating characteristics againstpredetermined operating characteristics assigned to said carburetor whenoperated in standard conditions.
 2. The portable analyzing device forcarburetors according to claim 1 including a switching mechanism tobypass inlet airflow to said vacuum pump and allow air to saidturbocharger to be pulled through a secondary air filter.
 3. Theportable analyzing device for carburetors according to claim 1 whereinin said drive belt includes a clutch.
 4. The portable analyzing devicefor carburetors according to claim 1 wherein said camera records videoor still shots of said carburetor's test fluid drawn through saidcarburetor.
 5. The portable analyzing device for carburetors accordingto claim 4 wherein said camera is adjustable when said carburetor ispositioned on said housing.
 6. The portable analyzing device forcarburetors according to claim 1 wherein said separator includes abaffle with a drip edge to remove fluid from the airstream.
 7. Theportable analyzing device for carburetors according to claim 1 whereinsaid turbocharger is capable of providing pressured air to replicate anengine mounted turbocharger.
 8. The portable analyzing device forcarburetors according to claim 1 wherein said vacuum pump utilizes animpeller providing an oil free continuous airstream within ananti-sparking cast aluminum housing.
 9. The portable analyzing devicefor carburetors according to claim 1 wherein said turbocharger providesa pressurized airstream to replicate a high rpm of about 2,700 rpmoperation.
 10. The portable analyzing device for carburetors accordingto claim 1 wherein said test fluid pump is a general aviation fuel pump.11. The portable analyzing device for carburetors according to claim 1including a monitor coupled to said computer system, said monitordisplaying said carburetor serial number and test results against astored test result, and storage of said test results.
 12. The portableanalyzing device for carburetors according to claim 1 wherein saidcamera allows for real time inspection of carburetor flow jets whiletest fluid is passing through said carburetor.
 13. The portableanalyzing device for carburetors according to claim 1 including acontrol valve to route said test fluid depending on fluid pressurerequired by said carburetor.
 14. The portable analyzing device forcarburetors according to claim 1 including an ultrasonic level indicatoris used to monitor the amount of test fluid in the fluid tank.
 15. Theportable analyzing device for carburetors according to claim 1 includinga flow transmitter and mass flow meter used to record test fluid flowrate.